Various operations and strategies may be used in hybrid vehicles to improve overall fuel economy. One approach utilizes regenerative braking where vehicle braking energy is stored for later use in propelling the vehicle. For example, in hybrid-electric vehicles, an electric machine may be at least partially coupled to the wheels/powertrain to provide braking torque by generating electrical energy that may be stored in a battery or other electric storage device. Thus, during later propulsion, the stored electrical energy may be converted to propel the vehicle, thereby saving fuel that would otherwise be spent in the engine, for example.
Because such regenerative braking systems may not generally provide sufficient braking performance for all vehicle operating conditions, hybrid vehicles may additionally utilize dissipative brake systems to brake the vehicle. For example, if a driver requests more braking than can be provided by the regenerative brake system, mechanical-friction wheel brakes may be applied on one or more wheels. In this way, sufficient vehicle braking performance can be provided.
However, the inventor herein has recognized a problem with such systems in practice especially when a particular class of drivers operate the vehicle. Specifically, some vehicle operators aggressively actuate the drive controls, such as the gas pedal and/or brake pedal, even when aggressive pedal or brake actuation may not be required. As a result, these operators typically achieve less fuel economy performance from hybrid vehicles because the aggressive brake actuation, for example, results in more dissipative braking than necessary, thus reducing the potential fuel economy gains achievable through regenerative braking.
The above issues may be addressed, in one example, by a system for a hybrid vehicle driver by an operator, comprising: an energy storage device; a regenerative braking system coupled to the energy storage device; a dissipative braking system coupled to the vehicle; a brake lever; a haptic operator interface; a control system for operating one or both of the regenerative and dissipative braking system in response to actuation of the brake lever, and providing feedback to the operator through the haptic interface differentiating a type of braking operation.
In this way, it may be possible to give feedback to the operator that indicates when driver braking actuation surpasses that which can be provided by the regenerative braking system, thus causing activation of dissipative braking. As such, the operator can learn by experience and real-time feedback how to apply less brake actuation for various conditions when possible to improve use of regenerative braking and thus improve vehicle fuel economy. In other words, the operator can learn at what point of brake actuation dissipative braking is applied for a given set of conditions, and can then adjust brake actuation, when possible to reduce use of the dissipative braking.
Note that various other alternatives approaches may also be used. For example, while a haptic interface may be advantageously used in some examples, on other examples visual and/or audio displays may also be used, and may be more advantageous in some cases. Also, the haptic or other feedback may be provided to the driver in various ways, such as when dissipative braking begins, or before dissipative braking is about to begin to provide the driver an opportunity to reduce braking, if possible, and avoid or reduce the dissipative braking. Further, various other alternative approaches may be used as described herein.